1. Field of the Invention
The present invention relates to a printing plate processing apparatus in which a photosensitive planographic printing plate is processed with processing solutions.
2. Description of the Related Art
As a photosensitive material, photosensitive planographic printing plates (hereinafter referred to as “PS plates”) comprising a photosensitive layer formed on an aluminum substrate or the like is used. In a PS plate processor which is a photosensitive material processing apparatus (printing plate processing apparatus) in which PS plates are processed, a plurality of processing steps which use processing solutions are provided: a developing step in which the PS plate is processed by being immersed in a developing solution; a washing step in which the PS plate is washed by spraying washing water onto the surface of the PS plate; a desensitizing step in which a desensitizing step is performed by coating the surface of the PS plate with a desensitizing solution such as a gum solution after the plate has finished the washing process; and the like. A PS plate which has undergone image exposure is thus subjected to developing, washing, and desensitizing processing, and the like in a processor such as this.
In the developing step of this PS plate processor, a printing plate is subjected to developing processing in such a manner as to be conveyed while being immersed in a developing solution stored in a developing tank. Further, the PS plate after it has finished the developing processing is nipped by a conveying roller pair provided at the most downstream side of the developing step and delivered to the subsequent washing step. At this time, in the PS plate processor, the PS plate is delivered to the washing step while the developing solution adhering to the surface of the PS plate is being squeezed out by the conveying roller pair.
In the conveying roller pair used to squeeze out the developing solution from the PS plate, a lower roller is partially immersed in the developing solution so as to prevent attached material on the surface of the PS plate from adhering to peripheral surfaces of the rollers and being transferred to the surface of a subsequent PS plate. In this type of conveying roller pair, a developing solution squeezed out from the PS plate, or a developing solution raised by the lower roller adheres to the peripheral surfaces of the rollers to form a solution film.
The developing solution used for processing of photosensitive material such as PS plates undergoes a deterioration in solution activity due to coming into contact with carbon dioxide (CO2) in the air. For example, the developing solution used for developing processing of PS plates contains components for dissolving silicate material or binder material. Due to the component coming into contact with carbon dioxide, the ability thereof for dissolving silicate material or binder material deteriorates.
As a result, silicate material or binder material causes generation of crystallized material which is hard to dissolve.
This crystallized material is also generated on a peripheral surface of a roller disposed outside the solution. That is, the developing solution adhering to the peripheral surface of the roller disposed outside the solution to form a solution film comes into contact with carbon dioxide in the air, thereby causing crystallized material generated by silicate material or binder material to appear as attached material on the peripheral surface of the roller. Further, the crystallized material increases as the amount of time that the developing solution comes into contact with carbon dioxide becomes longer.
The attached material on the roller is transferred to a PS plate which is to be subsequently processed, thereby exerting a great influence on the finished quality of a PS plate surface or on the printing performance.
In some photosensitive material processing apparatuses, a conveying roller pair is intermittently driven to rotate during a period in which photosensitive material is not processed, thereby causing surfaces of the rollers to be washed with a processing solution drawn by a lower roller (for example, see Japanese Patent Application Laid-Open (JP-A) No. 6-347975).
Further, in some of photosensitive material processing apparatuses, prior to processing of photosensitive material, a processing solution or processing solution component adhering to a peripheral surface of a lower roller disposed outside the solution in a conveying roller pair is washed off in such a manner as to be immersed in washing water, not in a processing solution such as a developing solution, or in such a manner that washing water is supplied to the peripheral surface of the roller (for example, see JP-A No. 9-281683).
However, in a case in which the rollers are merely driven to rotate intermittently, it is necessary to drive the rollers intermittently even when the operation of the apparatus stops. Further, in a case in which provision of a roller washing step in addition to a washing step by rollers is supposed, the structure of the developing step becomes complicated, and a developing solution in a developing tank is apt to come in contact with carbon dioxide in the air. Moreover, in a case in which the rollers are washed, the developing solution may be diluted due to the washing water.
The attached material on the roller adheres to a PS plate which has been processed first, and after the rollers make two or three revolutions, the attached material transferred to subsequent PS plates become diminished.
Accordingly, ordinarily, when the operation of a PS plate processor is started, a complicated operation is carried out in which a cleaning plate is inserted prior to insertion of a PS plate, and attached material adhering to the peripheral surface of a roller disposed outside the processing solution is transferred to the cleaning plate, or the like.